Justine Cohen1, Chantal E. Stern1; 1Boston University

Neuroimaging studies have shown increased activation in medial temporal and prefrontal brain regions while participants traverse critical points in overlapping mazes compared to non-overlapping mazes. In both humans and animals, theta rhythm has been theorized to play a role in spatial coding. Theta rhythm oscillations have been shown to increase in the prefrontal cortex in response to cognitively demanding tasks and are coherent with hippocampal oscillations. Based on an earlier fMRI design, we designed a task in which participants learned twelve mazes, three pairs that began and ended in distinct locations but converged in the middle to share a hallway (overlapping condition) and six distinct mazes (nonoverlapping condition). Each hallway within the mazes was lined with unique objects. One day after learning, participants returned for testing while undergoing EEG recording. Results showed that in the initial hallway, where participants were cued to which maze they were in, theta activity increased during the overlapping condition compared to the nonoverlapping condition. In addition, at the critical choice point – the end of the shared hallway in the overlapping condition - there was an increase in theta rhythm in overlapping compared to nonoverlapping mazes. Increases in theta activity coincided with time points where functional imaging using a similar task showed increased activation in hippocampus and prefrontal cortex. These results suggest that oscillatory dynamics in the hippocampus and prefrontal cortex are integral to disambiguation between mazes with overlapping routes.